1. Field of the Invention
The present invention relates to a process for producing a suspension component such as a link, an arm and the like used in a suspension of an automobile, and particularly, to a process for producing a suspension component made of light alloy such as aluminum alloy.
2. Description of the Prior Art
In automobiles, a light alloy such as an aluminum alloy has recently been employed even for arms as suspension components for the purpose of reducing the weight.
However, the suspension component is generally of a complicated shape. Therefore, if the component is intended to be formed into such a shape through a forging, a problem is encountered that it is necessary to use many dies through many steps, resulting in an increased manufacturing cost.
Thereupon, it has been conceived that in view of the fact that the light alloy is extrudable, a suspension component of a light alloy is Formed by an extrusion.
If the extrusion can be used in tills manner, a large number of the same components can be produced only by cutting the extruded product at a predetermined thickness, leading to a facilitated fabrication and a reduced manufacturing cost.
However, a shape which can be formed by the extrusion is limited only to a certain sectional shape which has no variation in an extruding direction. In most of the case, however, the suspension component is not formed into a shape with all of its individual portions directed to the same direction. For example, a suspension arm is pivotally connected at one end thereof to a vehicle body and at the other end to a wheel support member, respectively, through rubber bushes, but pivotal axes are not necessarily directed to the same direction, and in many cases, such axes may be directed to different directions. In such a case, it is required that axes of mounting bores provided in the suspension arm for press-fitting or fastening of the rubber bushes are directed to different directions. Therefore, even If the suspension arm is intended to be produced by an extrusion, It cannot be ensured that all of portions Including mounting bores can be formed by the extrusion.
Thereupon, in forming the suspension component by an extrusion, portions each having a direction different from an extruding direction such as bush mounting bores must be formed by a post-working. In such case, if the mounting bore, for example, the larger diameter mounting bore is intended to be formed vertically with respect to the extruding direction, the thickness of the component in the extruding direction must be larger than the diameter of the mounting bore. Moreover, it is required that a portion around the mounting bore has a strength enough to serve as a press-fitting portion or a fastening portion and hence, the thickness of such portion must be further increased. As a result, the entire component has an increased wall thickness, which is an obstacle to the reduction in weight.
From the above fact, it has been conventionally believed that little merit is obtained even if an extrusion is used for production of a suspension component.